Unreliable
Part of speech: adjective
Definition: Not reliable.
Example sentence: I absolutely don't want to suggest that women are unreliable because we're mothers - on the contrary. But the question of who brings up the kids has a material effect on all women's careers.
Irresponsible
Part of speech: noun
Definition: Someone who is not responsible.
Part of speech: adjective
Definition: Lacking a sense of responsibility; incapable of or not chargeable with responsibility; unable to respond to obligation.Not responsible; not subject to responsibility; not to be held accountable, or called into question.
Example sentence: Because war is a competition involving life and death, and in which national security and vital interests are at stake, establishing an objective other than winning is not only counterproductive, but also irresponsible and wasteful. In some circumstances, it is also unethical.